1. Field of the Invention
The present invention relates to ATM devices (e.g., switches and edge routers) used in telecommunication networks, and more specifically to a method and apparatus for managing the bandwidths of virtual circuits when the aggregate bandwidth to an adjacent device changes.
2. Related Art
Virtual circuits are often provisioned using asynchronous transfer mode (ATM) technology/standards as is well known in the relevant arts. In general, each of several pairs of ATM devices (switches, edge routers, etc.) are connected by corresponding one or more physical paths, and virtual circuits are provided using such connected pairs of ATM devices.
The aggregate bandwidth available from an ATM device to an adjacent ATM is typically shared by several virtual circuits. The bandwidths of virtual circuits generally determine the specific time points at which the cells related to respective virtual circuits are transmitted on the paths. Typically, cells related to virtual circuits with higher allocated bandwidths are provided turns for transmission with a correspondingly higher frequency.
In a prior embodiment, the bandwidth of a virtual circuit may remain unchanged even if the aggregate bandwidth to an adjacent ATM device changes. For example, the aggregate available bandwidth may be reduced as one of the paths becomes non-operational, but the bandwidth of various virtual circuits may remain unchanged. The bandwidth of the virtual circuits may not be similarly increased automatically if the aggregate bandwidth increases.
One problem with such an approach is that at least some of the virtual circuits may not get a fair share of available bandwidth when the aggregate bandwidth to the adjacent ATM device decreases. For example, some of the virtual circuits may hog (use all the available bandwidth) while the rest of the virtual circuits may have limited/no bandwidth to use. As a result, such rest of the virtual circuits may become unusable.
In the drawings, like reference numbers generally indicate identical, functionally similar, and/or structurally similar elements. The drawing in which an element first appears is indicated by the leftmost digit(s) in the corresponding reference number.